After instructing viewers to "put on your safety glasses", Nye launched into his plea.
"By the end of this century, if emissions keep rising, the average temperature on Earth could go up another four to eight degrees. What I'm saying is the planet's on f***ing fire," said Nye as he set fire to a wooden globe sitting on a disk in front of him.
"There are a lot of things we could do to put it out - are any of them free? No, of course not. Nothing's free, you idiots.
"Grow the f*** up. You're not children anymore. I didn't mind explaining photosynthesis to you when you were 12. But you're adults now, and this is an actual crisis, got it? Safety glasses off, motherf***ers."
Nye proceeds to blow on the globe which is still sizzling as he storms off.
In another segment, host John Oliver enlists the science educator to help explain carbon pricing - a proposal to charge emitters of greenhouse gases more for their pollution.
And while the initial reasoned response was more like the Nye of old, his closing remarks were both hilarious and shocking.
"When we release carbon, say, by burning coal or driving an SUV, all of us pay for that in the form of things like fires, floods and crop failures," Nye said.
"Putting a fee on carbon creates incentives to emit less carbon, and, more importantly, it also incentivises the development of low-carbon technology, which is huge, because that's vital to reducing emissions globally."
But Nye wasn't done yet.
"And because for some reason, John, you're a 42-year-old man who needs his attention sustained by tricks, here's some f***ing Mentos and a bottle of Diet Coke. Happy now?"
The segments were part of Last Week Tonight's 'Green New Deal' topic, a proposal put forth by freshman US Representative, Alexandria Ocasio-Cortez, with John Oliver highlighting various models of helping to slow the funneling of greenhouse gases into Earth's atmosphere, like carbon cap and trade and a carbon tax.
